Considering that fossil raw materials are likely to become more scarce in the future, processes are gaining interest which make possible the utilization of electrical energy in energy-consuming processes which electrical energy can be generated on a non-fossil basis, e.g., nuclear energy or renewable resources such as hydrodynamic power and solar energy. If such energy is required at high temperatures, electric arc or plasma processes are particularly suitable. Thus, the production of acetylene from gaseous and liquid hydrocarbons has been known for years and is conducted on a commercial scale (Gladisch, Hydrocarbon processing, Petroleum Refiner 41, No. 6, 159 to 164 (1962)). In that process, only about 50% of the fossil raw material requirements are saved as compared with processes based entirely on fossil materials, such as for example partial oxidation. In recent years, development work has commenced with a view to also producing acetylene from coal in an electric arc or plasma process (D. Bittner, H. Baumann, C. Peuckert, J. Klein, H. Juntgen, Erdol und Kohle Erdgas-Petrochemie 34, issue 6, 237 to 242 (1981)).
A further reaction in which plasma processes have been applied is the reforming of hydrocarbons or coal by means of a gasification medium such as steam or carbon dioxide to form a gas mixture composed predominantly of CO and H.sub.2. The latter finds wide technical use in the chemical industry as synthesis gas or in the metallurgical industry as reduction gas. Here, as well, the employment of the electric arc process permits a savings of about 50% of the direct fossil energy requirements.
In the pyrolysis of coal in the plasma process it is possible to derive substantially larger amounts of volatile matter from the coal than in conventional coking processes. A yardstick for the proportion of compounds which may ordinarily be recovered is the content of so-called "volatiles" of the coal which is determined under standardized assay conditions (DIN 51 720 or ISO 562).
In plasma pyrolysis, a yield of volatile compounds can be recovered exceeding by a factor of approximately 2 the "volatile" content of the coal. In that case these volatiles are composed predominantly of C.sub.2 H.sub.2 and CO. Coke is left behind as a residue. However, in large scale practice there are obtained some 1 to 2t of coke/t C.sub.2 H.sub.2. This must be disposed of. If this coke is combusted in a power plant, this permits about 50% of the electrical energy requirements for the acetylene production to be generated--being in the region of 10 kWh/kg C.sub.2 H.sub.2. However, as a result, a major part of the advantage of an electric arc process is lost, i.e., the co-use of electrical energy on a non-fossil basis.